Outward-looking houses: the "Dowlat abad" Garden.

Comprising a large garden and some buildings, the "Dowlat abad" Garden is a famous complex built in the original Iranian style which was watered by a qanat of the same name. In the past, it was the residence of the governor. The most impressive part of this complex is the main building, that is an example of Outward-Looking houses in Yazd, with a complete ventilation system. The main part of this system is the very tall badgir (opposite) with a hieght of 33.35meters and an octagonal plan. This badgir catches cool winds at a higher level, in all directions, and channels them into the interior spaces. The dry and warm wind will pass over a pond with a fountain gets cool and wet through evaporation. Then the cool and wet air flows in the room. There is an increase in air pressure to windward and decrease to leeward, so the badgir will catch the windward air and sucks the interior air to leeward, thus ventilating the interior.

The badgir's material again plays another role, the temperature differences between day and night is quite high in this climate, the day 35 degree centigrade and night with 17 degree centigrade, so they use this high fluctuation of temperature. At night time when it is cold the badgir, which is made with mud-brick, gets cool by radiation and convection.

The mud-brick has 7 to 9 hours response time So in the morning it begins to give its coolness to air so the internal air becomes cold and because of its high density, flows down in the rooms.

This happens in the morning. The wind shaft gets warm during the daytime, at night it works as a solar chimney, the walls will give their heat to the air, with that delay, and the internal air decreases in density, rises and sucks the air in the room. Cool air will then replace warm air in the room. The system works, when there is no wind, but when wind is blowing this system does not have problems. Because during the day, if there is wind, then cool air flows faster and at night, with wind, it may absorb the heat of the walls, because the night wind is cool enough.